1. Field of the Invention
The invention relates generally to an electrophysiological (xe2x80x9cEPxe2x80x9d) apparatus and method for providing energy to biological tissue, and more particularly, to a steerable catheter with an adjustable curved distal shape for positioning the catheter to a desired location in a patient.
2. Description of the Related Art
The heart beat in a healthy human is controlled by the sinoatrial node (xe2x80x9cS-A nodexe2x80x9d) located in the wall of the right atrium. The S-A node generates electrical signal potentials that are transmitted through pathways of conductive heart tissue in the atrium to the atrioventricular node (xe2x80x9cA-V nodexe2x80x9d) which in turn transmits the electrical signals throughout the ventricle by means of the His and Purkinje conductive tissues. Improper growth of, or damage to, the conductive tissue in the heart can interfere with the passage of regular electrical signals from the S-A and A-V nodes. Electrical signal irregularities resulting from such interference can disturb the normal rhythm of the heart and cause an abnormal rhythmic condition referred to as xe2x80x9ccardiac arrhythmia.xe2x80x9d
While there are different treatments for cardiac arrhythmia, including the application of anti-arrhythmia drugs, in many cases ablation of the damaged tissue can restore the correct operation of the heart. Such ablation can be performed by percutaneous ablation, a procedure in which a catheter is percutaneously introduced into the patient and directed through an artery to the atrium or ventricle of the heart to perform single or multiple diagnostic, therapeutic, and/or surgical procedures. In such case, an ablation procedure is used to destroy the tissue causing the arrhythmia in an attempt to remove the electrical signal irregularities or create a conductive tissue block to restore normal heart beat or at least an improved heart beat. Successful ablation of the conductive tissue at the arrhythmia initiation site usually terminates the arrhythmia or at least moderates the heart rhythm to acceptable levels. A widely accepted treatment for arrhythmia involves the application of RF energy to the conductive tissue.
In the case of atrial fibrillation (xe2x80x9cAFxe2x80x9d), a procedure published by Cox et al. and known as the xe2x80x9cMaze procedurexe2x80x9d involves continuous atrial incisions to prevent atrial reentry and to allow sinus impulses to activate the entire myocardium. While this procedure has been found to be successful, it involves an intensely invasive approach. It is more desirable to accomplish the same result as the Maze procedure by use of a less invasive approach, such as through the use of an appropriate EP catheter system.
One such EP catheter system, as disclosed in U.S. Pat. Nos. 6,059,778 and 6,096,036, includes a plurality of spaced apart band electrodes located at the distal end of the catheter and arranged in a linear array. The band electrodes are positioned proximal heart tissue. RF energy is applied through the electrodes to the heart tissue to produce a series of long linear lesions similar to those produced by the Maze procedure. The catheters currently used for this procedure are typically flexible at the distal end, and the profile at the distal end is adjustable. However, when using such catheters, it is often difficult to conform the distal end profile to some of the irregular topographies of the interior cavities of the heart. In other instances, it is difficult for a multi-electrode catheter that is designed to produce long linear lesions to access and ablate tissue in regions that require short linear lesions, such as the so-called isthmus region that runs from the tricuspid annulus to the eustachian ridge. Ablation of tissue in this region, and other regions non-conducive to the placement of multi-electrode, long, linear-lesion ablation catheters within them, is best accomplished by delivering RF energy to a tip electrode to produce localized spot lesions or tip-drag lesions.
Proposed methods of ablating irregular topography areas and regions, such as the isthmus region, use a rigid introducer sheath in combination with a tip-electrode ablation catheter. The introducer sheath is used to position the tip electrode in the proper location. Once positioned, the electrode is either held in place by the sheath to produce a spot lesion or is dragged along the surface of the tissue, by the sheath, to produce a tip-drag lesion. The disadvantage of this system is that it requires the use of two instruments: the introducer sheath and the catheter. The use of an introducer sheath increases both instrument cost and patient trauma.
Other catheters for producing spot lesions or tip-drag lesions typically comprise a tip ablation electrode and a plurality of mapping band electrodes positioned at the distal end of the catheter. The catheters are steerable in that they are configured to allow the shape of the distal end of the catheter to be manipulated from a location outside the patient""s body. Steerable catheters that produce multiple bending profiles provide a broader range of steerability. However, known steerable catheters such as that disclosed in U.S. Pat. No. 5,195,968 have steering tendons attached to a ribbon, at or near the longitudinal centerline of the catheter. Because these tendons are fixed in place, the catheter is capable of providing only two types of steering profiles. As such, its ability to ablate within a biological site having cavities of various different shapes and sizes is limited.
Hence, those skilled in the art have identified a need for a catheter having a steerable distal-end region that is not limited to a select few deflection profiles but rather a variety of different profiles to improve access to difficult-to-reach locations of the human body. The present invention fulfills these needs and others.
Briefly, and in general terms, the invention is directed to an electrophysiological (xe2x80x9cEPxe2x80x9d) catheter with a steerable, multi-profile distal-end region for maneuvering through and positioning within irregular topographic and difficult-to-reach locations of the human body.
In a first aspect, the invention relates to a catheter having an elongated tubular sheath with a proximal region, a distal-end region and a lumen therebetween. The catheter also includes a steering tendon having a first end coupled to the distal-end region of the sheath and a second end located at the proximal region of the sheath. Movement of the steering tendon in a proximal direction causes the sheath distal-end region to deflect. The catheter further includes a core that is disposed within the lumen of the sheath. The core includes a proximal end and a distal end. A distal portion of the core includes a curved shape. The core is longitudinally adjustable relative to the sheath to effect deflection of the distal-end region of the sheath.
In a detailed aspect of the invention, the core is formed of a shape-memory material. In another detailed aspect, the core includes a substantially tubular structure having a lumen. At least one electrode is positioned at the distal-end region of the sheath. The at least one electrode is electrically connected to wires which pass through the lumen of the core. The steering tendon also passes through the lumen of the core. In a further detailed aspect, the core includes a solid wire. In this aspect, the steering tendon and the wires that are connected to the at least one electrode are carried within grooves located on the outside of the core and on the inside wall of the sheath. In an additional aspect of the invention, the relative rigidity of the sheath proximal region, sheath distal-end region and core is such that when the core is within the sheath proximal region, the core assumes the shape of the sheath proximal region. Further, when the curved distal portion of the core is within the sheath distal-end region, the sheath distal-end region assumes the shape of the curved distal portion of the core. In yet another detailed aspect of the invention, the catheter also includes a positioning mechanism that is secured to the core and is adapted to move the core between locations within the proximal region of the sheath and the distal-end region of the sheath. In one facet, the core may be moved to a fully retracted position wherein the distal end of the core is located within the proximal region of the sheath such that movement of the steering tendon in a proximal direction causes the entire distal-end region of the sheath to deflect into a tight loop. In another facet, the core may be moved to an advanced position wherein a section of the distal portion of the core is located within the distal-end region of the sheath. In this facet, movement of the steering tendon in a proximal direction causes the radius of curvature of the portion of the distal-end region housing the core to decrease and the portion of the distal-end region of the sheath distal to the core to deflect into a tighter radius than if the core were not present. In a further facet, the deflection profile of the distal-end region of the sheath is adjustable by changing the location of the distal end of the core within the distal-end region of the sheath.
In a second aspect, the invention relates to a catheter having an elongated tubular sheath having a proximal region, a distal-end region and a lumen therebetween. The catheter also includes a steering tendon having a first end coupled to the distal-end region of the sheath, and a second end located at the proximal region of the sheath. Movement of the steering tendon in a proximal direction causes the sheath distal-end region to deflect. A core is disposed within the lumen of the sheath. The core includes a proximal end and a distal end, and a distal portion of the core includes a curved shape. The core is longitudinally adjustable relative to the sheath, thereby effecting deflection of the distal-end region of the sheath. A handle is coupled to the proximal region of the sheath. The handle includes a positioning mechanism for moving the core. The catheter also includes at least one electrode located within the distal-end region of the sheath. The at least one electrode is electrically connected, by wires, to a connector within the handle.
In a third aspect, the invention relates to a method for placing the distal portion of a catheter at a desired location within a biological cavity. The catheter used in the method includes an elongated tubular sheath having a proximal region and a distal-end region. The catheter also includes a steering tendon having a first end coupled to the distal-end region of the sheath and a second end located at the proximal region of the sheath. The catheter further includes a longitudinally adjustable core that is disposed within the lumen of the sheath. A distal portion of the core has a curved shape. The relative rigidity of the sheath proximal region, sheath distal-end region and core is such that when the core is within the sheath proximal region, the core assumes the shape of the sheath proximal region. Further, when the curved distal portion of the core is within the sheath distal-end region, the sheath distal-end region assumes the shape of the curved distal portion of the core. The method includes introducing the catheter into a body vessel with the curved distal portion of the core located in the sheath proximal region. The method also includes advancing the catheter through the vessel into the biological cavity. The method further includes deflecting the distal-end region of the catheter toward the desired location by advancing the curved distal portion of the core into the sheath distal-end region. In a detailed aspect of the invention, deflecting the distal-end region of the catheter further includes axially displacing the steering tendon in a proximal direction.
These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings which illustrate by way of example the features of the invention.